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CSIR NET Maths

How candidates actually lose marks

A worked solution tells you the right answer. It does not tell you why the answer you chose looked right — which is the only question worth asking after getting one wrong.

We work through the wrong options on this site and name the specific mistake that produces each one — 2247 of them so far. 2002 fall into the 13 kinds of error that actually repeat; the other 245 are one-offs. The families are ranked below by how often each one appears — not by how important it sounds.

2247 wrong options analysed2002 in 13 families201 readable free
  1. 01
    Execution slip971 wrong options · Part A, B, C

    The idea was right. The computation was not.

  2. 02
    Hypothesis dropped266 wrong options · Part A, B, C

    A theorem applied without checking one of its preconditions.

  3. 03
    Boundary and endpoint226 wrong options · Part A, B, C

    The statement turns at the edge of the interval, the domain, or the parameter range.

  4. 04
    Standard counterexample213 wrong options · Part A, B, C

    There is a canonical object that settles this. Recognising it is the whole question.

  5. 05
    Converse assumed79 wrong options · Part A, B, C

    The theorem runs one way. You used it in the other.

  6. 06
    Invariants don't determine40 wrong options · Part A, B, C

    Two objects sharing an invariant were treated as the same object.

  7. 07
    Limit assumed to exist37 wrong options · Part A, B, C

    Reasoning with a limit before establishing there is one. limsup is not lim.

  8. 08
    Property not inherited37 wrong options · Part B, C

    A property assumed to pass to subobjects, quotients, or through a chain. It does not.

  9. 09
    Pointwise vs uniform34 wrong options · Part B, C

    The mode of convergence — or of continuity — was the wrong one.

  10. 10
    Base field or ring26 wrong options · Part B, C

    The answer changes with the field or ring you are working over.

  11. 11
    Dependence misread26 wrong options · Part A, B, C

    Independence, pairwise vs mutual, or correlation vs dependence.

  12. 12
    Moments and tails26 wrong options · Part B, C

    A moment assumed to exist, or tail behaviour assumed to be tame.

  13. 13
    Existence vs uniqueness21 wrong options · Part B, C

    A theorem giving one was read as giving both.

Which of these catches you?

Take a mock and the review names the mistake behind every wrong answer — not the topic, the reasoning error. Repeat it across papers and the pattern is usually three or four families, not fifty topics.

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Common questions

What are the most common mistakes in CSIR NET Mathematical Sciences?
They are mistakes of reasoning rather than of topic, and they repeat. The families collected on this page are the recurring ones: applying a theorem outside the hypothesis it needs, treating a boundary case as though it were generic, confusing a condition with its converse, and arithmetic slips under time pressure. A candidate who keeps losing marks usually has three or four of these, not fifty weak topics.
Why do I keep picking the wrong option even when I know the topic?
Because the wrong options are constructed, not random. Each one is built to be what you get if you make a specific error — the answer you would reach having forgotten one hypothesis. Knowing the topic does not protect you from that; noticing which error the option was built from does.
Does negative marking make guessing a bad idea in CSIR NET?
Only blind guessing. Part A deducts 0.5 against 2 for a correct answer and Part B deducts 0.75 against 3, so a question narrowed to two options has positive expected value in both. Guessing across four does not. Part C has no negative marking at all, but awards nothing unless you select exactly the correct set.
How do I stop making the same mistake in Part C?
Part C is scored all-or-nothing across multiple correct options, so ruling an option out is worth exactly as much as ruling one in. That makes it the part where a single unexamined habit costs whole questions rather than fractions of a mark. Working through wrong options sorted by the mistake behind them — rather than by topic — is what makes the habit visible.
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